Electric Motor Cost/Watt Is Impervious To Size

[Bret Cahill]

There doesn't seem to be much in the way of economies of scale when it comes to the cost/watt of electric motors.

Most 50 kW motors cost between 6 cents / watt and 20 cents / watt.

Most 1 kW motors cost between 6 cents / watt and 20 cents / watt.

Is this simply a matter of materials volume/ weight and therefore costs are linear with power?


Bret Cahill

 

[Tim Wescott]

On Mon, 30 Jan 2017 10:49:23 -0800, Bret Cahill wrote:

There doesn't seem to be much in the way of economies of scale when it
comes to the cost/watt of electric motors.

Most 50 kW motors cost between 6 cents / watt and 20 cents / watt.

Most 1 kW motors cost between 6 cents / watt and 20 cents / watt.

Is this simply a matter of materials volume/ weight and therefore costs
are linear with power?

Is that just within a technology, like PM DC motors? Or are you
including induction motors as well?

Most motors are pretty much limited by physics, to the point where,
within a category, you can weigh one and make a good guess of its power
capability.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

 

[Bret Cahill]

There doesn't seem to be much in the way of economies of scale when it
comes to the cost/watt of electric motors.

Most 50 kW motors cost between 6 cents / watt and 20 cents / watt.

Most 1 kW motors cost between 6 cents / watt and 20 cents / watt.

Is this simply a matter of materials volume/ weight and therefore costs
are linear with power?

Is that just within a technology, like PM DC motors? Or are you
including induction motors as well?

As long as it isn't some specialty motor, that doesn't seem to matter much either.

Most motors are pretty much limited by physics, to the point where,
within a category, you can weigh one and make a good guess of its power
capability.

Not that it reduces cost/kW but rare earth magnet motors supposedly have a higher power to weight ratio.

Anyway, back to the issue. As much as copper costs, a working motor fetches at least an order of magnitude more than the same motor sold as scrap metal.

It seems like the production costs of such a high volume item would have been tweaked until the cost of the motor wouldn't be too much more than materials costs.


Bret Cahill

 

[Tim Wescott]

On Mon, 30 Jan 2017 21:03:42 -0800, Bret Cahill wrote:

There doesn't seem to be much in the way of economies of scale when
it comes to the cost/watt of electric motors.

Most 50 kW motors cost between 6 cents / watt and 20 cents / watt.

Most 1 kW motors cost between 6 cents / watt and 20 cents / watt.

Is this simply a matter of materials volume/ weight and therefore
costs are linear with power?

Is that just within a technology, like PM DC motors? Or are you
including induction motors as well?

As long as it isn't some specialty motor, that doesn't seem to matter
much either.

Most motors are pretty much limited by physics, to the point where,
within a category, you can weigh one and make a good guess of its power
capability.

Not that it reduces cost/kW but rare earth magnet motors supposedly have
a higher power to weight ratio.

Anyway, back to the issue. As much as copper costs, a working motor
fetches at least an order of magnitude more than the same motor sold as
scrap metal.

It seems like the production costs of such a high volume item would have
been tweaked until the cost of the motor wouldn't be too much more than
materials costs.

My understanding is that winding coils is a hard job for machines. So
it's either done by hand or by machines that need a lot of maintenance.

So at least in the short term, if the robots take over the world they'll
need to keep us around to make their motors.

--
Tim Wescott
Control systems, embedded software and circuit design
I'm looking for work! See my website if you're interested
http://www.wescottdesign.com

 

[Bret Cahill]

There doesn't seem to be much in the way of economies of scale when
it comes to the cost/watt of electric motors.

Most 50 kW motors cost between 6 cents / watt and 20 cents / watt.

Most 1 kW motors cost between 6 cents / watt and 20 cents / watt.

Is this simply a matter of materials volume/ weight and therefore
costs are linear with power?

Is that just within a technology, like PM DC motors? Or are you
including induction motors as well?

As long as it isn't some specialty motor, that doesn't seem to matter
much either.

Most motors are pretty much limited by physics, to the point where,
within a category, you can weigh one and make a good guess of its power
capability.

Not that it reduces cost/kW but rare earth magnet motors supposedly have
a higher power to weight ratio.

Anyway, back to the issue. As much as copper costs, a working motor
fetches at least an order of magnitude more than the same motor sold as
scrap metal.

It seems like the production costs of such a high volume item would have
been tweaked until the cost of the motor wouldn't be too much more than
materials costs.

My understanding is that winding coils is a hard job for machines. So
it's either done by hand or by machines that need a lot of maintenance.

That would tend to increase the $/watt of smaller motors.

One suspect theory is that the economy of volume production of smaller motors cancels out the economy of scale of low volume larger motors.

Here's a used motor, a high volume production 80 kW traction motor for $500:

http://www.ebay.com/itm/2012-NISSAN-LEAF-Electric-Traction-Motor-EM61-38K-Tested-Warranty-OEM-Autogator/122269966743?_trksid=p2047675.c100010.m2109&_trkparms=aid%3D333008%26algo%3DRIC.MBE%26ao%3D1%26asc%3D20131231133846%26meid%3D4f390ab2e79c4c3587e2e96d96651eb5%26pid%3D100010%26rk%3D1%26rkt%3D6%26sd%3D252539061797

It is about an order of magnitude cheaper than the range given above so it is an outlier. A third of the delivered cost is shipping so it must weigh something.

So at least in the short term, if the robots take over the world they'll
need to keep us around to make their motors.